The present invention relates to an improvement in the structure of a hydraulic anti-lock brake system which is to be fixed between a master cylinder and a cylinder pipe for feeding brake fluid pressure to the brake mechanism of automobile wheels, and more particularly to a device that accumulates or stores a part of the fluid pressure to be transferred to the wheels upon braking of the automobile, and then continuously feeds the fluid pressure by dividing so that the locking phenomena of brakes, produced upon sudden quick braking, is prevented, thereby preventing loss of steering control, and the like. More particularly, it relates to an article made such that the expansion rate of a resiliently expandable bulb is maximized by making the expanding direction of the bulb to be concentrated to one direction when the bulb is expanded by feeding of hydraulic pressure, so that not only the life of the bulb is extended, but also separate spring and spring protecting structure upon feeding excessive pressure, as well as a supporting tube for minimizing the friction upon operating, are provided, whereby stored hydraulic pressure can be resiliently and more strongly fed by dividing, and also damage of parts can be prevented upon feeding an excessive pressure, and at the same time the friction coefficient between the interior surface of the body and parts is decreased, so that not only the life of the parts is extended, but also the operating effect is furthermore improved.
Heretofore a number of techniques for hydraulic anti-lock brake systems have been patented and are known, for instance, U.S. Pat. No. 3,430,660 to Mitton; U.S. Pat. No. 4,571,009 to Jones; and U.S. Pat. No. 5,074,625 to Jones, and when reviewing their common structure, as shown in FIG. 1, a bulb 3 of rubber material is provided between upper body 1 and lower body 2, and a spatial portion 4 into which the expanding portion of the bulb 3 is inserted, and into which the volume of the bulb 3 can be expanded, is defined at the interior circumferential surface of the lower body 2, and when a pedal is pushed in order to apply the brake, hydraulic pressure of the brake is transferred to the brake mechanism of the wheel and to the hydraulic pressure inducing chamber 3' of the bulb, and the bulb 3 is expanded in volume toward the spatial portion 4 of arc shape, that is, the bulb 3 has the effect of storing a part of the hydraulic pressure, and even if the pedal is pushed with all one's might, a part of the produced hydraulic pressure is stored in the bulb, and therefore, a locking phenomena of the brake is prevented.
On the other hand, when the hydraulic pressure is consumed during operation of the brake, and it becomes lower than the stored pressure of the bulb 3, immediately the bulb 3 contracts and simultaneously a hydraulic pressure in the amount of the pressure difference is supplied, and this operation is repeated normally several times, to several tens of times, per second.
Accordingly, the conventional bulb operated by expanding in all directions in compliance with the thus continuous repeating process of expansion and contraction has had a problem that material deformation of the bulb, and deterioration of the resiliency, are rapidly increased, whereby the hydraulic pressure storing rate is decreased and the life is shortened. Since the rate of expansion and contraction becomes lowered in response to usage, it has also a problem that the dividing and feeding of the hydraulic pressure become less rapid, and at the same time the feeding pressure of the hydraulic pressure becomes lowered, whereby the braking distance of the brake systems becomes longer.